This invention concerns a method to extract and deposit coils in a rolling line and concerns also the device that performs the method.
The invention is applied advantageously to the field of iron metallurgy and, in particular, downstream of a coiling machine installed in line with a plant carrying out rolling of rod, the plant including at least one step of in-line thermal treatment of the rolled stock.
Coiling machines installed at the outlet of a rolling line producing rod, which is thereafter coiled on reels, are known in the state of the art.
In the plants of the state of the art the hot rod coming from the rolling line is coiled in spirals in a coiling machine; the coils leaving the coiling machine fall regularly and naturally onto a downstream removal conveyor belt.
The coils are arranged partly superimposed on each other and lying on the substantially horizontal surface of the removal conveyor belt, which delivers the coils to a winding means.
In normal plants for winding in the hot state, the coils forming the leading and trailing-ends fall upright onto the belt and then arrange themselves parallel to the removal conveyor belt.
Where the products are treated thermally in line with a surface hardening treatment, which causes the rolled stock to have its leading and trailing ends cold or where other particular thermal treatments are carried out which bring the strength of the rod up to values of about 400 N/mm.sup.2 or even up to 700 N/mm.sup.2, the process of forming the coils in the coiling machine entails a series of problems.
In particular, the leading coils leaving the coil-forming head of the coiling machine do not drop along the conveyor belt but have a tendency to stay upright at a right angle to the removal conveyor belt and to proceed along a given segment of the belt like a spring having a horizontal axis.
These leading-end coils tend to keep the other coils too in that position and cause a great obstruction in the end and make it impossible to carry out the winding.
The trailing-end coils behave in a like manner and also stay upright at a right angle to the conveyor belt, thus making impossible the next step of collecting the coils.
In plants which carry out in-line thermal treatment of the rolled products, in order to make possible the correct falling of the leading and trailing-end coils on the removal conveyor belt, the solution has been adopted of making these leading and trailing-end coils arrive in the hot state at the coil-forming means, whereas all the other intermediate coils arrive there cold.
This makes necessary the disposal and elimination of the leading and trailing-end coils, thus entailing a great waste of material which may involve losses even of some tons of material.
Moreover, with the plants of the state of the art it is impossible to wind rods having a high strength of about 600 N/mm.sup.2, for instance.
Patent GB-A-1,056,915 discloses a device to wind hot rolled products which is positioned at the exit of the rolling line; this device includes a coil-forming assembly associated downstream with means of a rotary chain type which convey coils.
These means to convey coils are suitable to engage one coil at a time and make it pass into a cooling chamber, thereafter positioning it on finger means positioned circumferentially in cooperation with the upper end of a collection block on which the coils are collected.
These finger means have the task of cooperating with the coil-collection block in the winding step and are positioned in a contact position where they retain the coils when the collection block has to be permitted to be lowered and removed from the device when the winding process has ended, the fingers remaining there for the whole time necessary to re-position a new coil-collection block.
This winding device works with hot products which do not cause the problems linked to the strength of the leading and trailing-end coils as mentioned above.
Moreover the finger means are not positioned in cooperation with the coil-forming assembly and do not act on the coils just formed but cooperate with the coil-collection block after the coils have passed through the whole cooling chamber and during the step in which the coils are laid on the coil-collection block.
U.S. Pat. No. 4,168,993 is also known and includes a coil-forming assembly that discharges the coils onto a conveyor belt, on which the coils are subjected to a cooling process by means of high-velocity water jets acting on the coils from below.
The coils subjected to the action of the jets may undergo a displacement due to the high speed and high pressure at which the water is sprayed.
This document therefore includes an open chain conveyor placed above the conveyor belt and having the task of accompanying the coils to keep them in position and to prevent any displacement thereof.
This document too works with hot products which do not suffer the above problems inasmuch as the hot coils have a natural tendency to remain deposited on the belt, and only the occurrence of an external factor may cause the displacement of the coils from their correct position on the conveyor belt.
Moreover, the open chain conveyor does not have the task of flattening coils which tend to rise again and to stay upright owing to natural causes, but has the task of retaining the correct position of the coils on the conveyor belt when the coils are displaced upwards as a result of the action of the jets acting from below.